Method for the ultrasonic flaw detection of an electric welded pipe

Abstract

An ultrasonic flaw detection method in which defects in the weld zone of an electric resistance welded steel pipe are detected by projecting an ultrasonic wave (a) having a frequency range of from 25 MHz to 500 MHz at an angle of incidence of from 0 DEG to 12 DEG onto the weld zone of the pipe. In addition by projecting another ultrasonic wave (b) having a frequency of from 2 MHz to 10 MHz at an angle of incidence of from 15 DEG to 27 DEG onto the same weld zone enables discrimination between cold weld defects and other defects such as inclusions and penetrators.

We claim: 
     
       1. A method for ultrasonic flaw detection of flaws in the weld zone of an electric resistance welded pipe, comprising: projecting an ultrasonic wave beam having a frequency in the range of 25 MHz to 500 MHz onto the outer surface of said weld zone at an angle of incidence to a perpendicular to the tangent to said pipe at the weld zone, which angle is between 0° and 12°,   whereby cold weld defects, inclusions and penetrators in the weld zone are detected.   
     
     
       2. A method as claimed in claim 1 in which said wave beam is projected by a probe, and said probe is moved so as to scan back and forth across said weld zone in a distance range of 10 mm on each side of said weld zone. 
     
     
       3. A method as claimed in claim 1 further comprising projecting an ultrasonic wave beam having a frequency in the range of 2 MHz to 10 MHz onto the outer surface of said weld zone at an angle of incidence to said perpendicular which is between 15° and 27° for detecting inclusions and penetrators, and discriminating signals produced as a result of the projection of the respective wave beams for determining from the signal resulting from the firstmentioned wave beam which of the flaws detected thereby are cold weld defects.